Google's Cloud Platform is becoming more open and more accessible to newcomers.

Last week, Google said App Engine users can now run Java App Engine applications in a private cloud using JBoss CapeDwarf, an implementation of the Google App Engine API that supports deployment on JBoss Application Servers.

Vendor lock-in has long been a concern among those who develop cloud applications, as it was when Google launched App Engine in 2008. But a year later, there was an escape hatch, in the form of AppScale, an open source App Engine implementation.

Nevertheless, potential cloud customers remain wary about being trapped. "We hear consistently from developers that they want to see more portability of their apps when working in the cloud," said Google engineer Ludovic Champenois in a blog post on Thursday.

The ability to run App Engine apps in a private cloud via CapeDwarf represents an attempt to address lock-in concerns, as does Google collaboration with JBoss owner Redhat to develop the open source Test Compatibility Kit (TCK) project. The TCK provides a way to test whether App Engine code can run on third-party infrastructure without modification.

Having recently added PHP support to App Engine, a move seen as an effort to make App Engine more popular, Google is continuing its effort to broaden the appeal of its platform-as-a-service offering by introducing a service called Cloud Playground.

Cloud Playground provides a way to test the App Engine APIs directly from Google's developer website, through the addition of green "Run/Modify" buttons that now accompany App Engine code examples.

Previously, developers wishing to run code on App Engine had to set up a local development environment, then upload the code and deploy it to test anything. It's not a particularly difficult process, but it can be frustrating if the code has bugs or isn't properly configured.

Cloud Playground provides instantaneous feedback. It allows developers to enter a few lines of Python code and run the program immediately. Better still, it provides a way to easily modify sometimes lengthy snippets of sample code to learn how App Engine responds, all without the potentially deterrent burden of setting up an account or logging in.

The experimental service also supports sharing: Users can copy the URL of their online workspace and send it to friends and colleagues, who can then review the code and modify it. In addition, it allows users to enter Github project URLs to import project code from Github into the Cloud Playground.

There's no doubt Google has made headway into businesses: Just 28 percent discourage or ban use of its productivity ­products, and 69 percent cite Google Apps' good or excellent ­mobility. But progress could still stall: 59 percent of nonusers ­distrust the security of Google's cloud. Its data privacy is an open question, and 37 percent worry about integration.